Behavior change

[Kimberly Price <PLOUGH1@ix.netcom.com>]

Hello ridecampers, could you help me worry (hopfully, needlessly), about
Mystery's behavior change:

New behavior:   Trembles and muscles spasms when asked to load.
Especially in his shoulders, chest area, little on the hind muscles.
Loads fine, does not protest (hops in!), plenty of energy on the trail,
displays some more muscle trembling and spasms when excited about "lets
get going".  Usually pees at the beginning of a ride once he is warmed
up, is not doing this anymore since this behavior started.    Weather is
warm, I think it is excitment, apprehension, anticipation(?).  I fear
thumps or metabolic problems.  When he does pee, liquid is normal.  No
stiffness.

What I "think" it is:    Hes traveled in a slant load with no divider
this year.  I think with the divider up it is too narrow for him.
Traveling with a friend on a 5 hour trip (we did stop) I had the divider
up.  New behavior "seemed" to start around this time.

He has free access to salt, gets good quality pasture grass (rye), some
Ovalene 200, plenty of energy on the trail..in fact...acts in the best
shape he's ever been in.  We've had a lot of just FUN lately, he is
really enjoying the trail.  No more saddle problems, comes to me in
pasture (like a good arab!).

I will have blood drawn if behavior continues to check for imbalances in
??? (salts?).   My gut feeling is he is just getting excited, but he is
11 years old and has never displayed this behavior before..why start now
if it is a mental thing?!

Do I have my bases covered or could something else be going on?

Thanks!
Kimberly (&Mystery the Morab...."lets go, lets go, come ON! Lets GO!")
Pt.Reyes, CA